It appears that overseas based CAs are now assigned to long haul flights - NRT-KOA by BKK CAs; DFW-HND by TPE CAs; NRT-MEL by BKK CAs. Their service is exceptional on my recent flights with JAL.
P.S. the Japanese economy class supervisor on JL773 NRT-MEL (10 Apr) was very rude (to my surprise)! First time I see a JAL crew bowing to the wall of the galley rather than to passengers when the welcoming announcement / safety video is played. While other crews were super friendly assisting passengers, she leaned on the cabin wall doing nothing but just loudly commanding the other crews to do everything. Feel bad for the other crews who have done an outstanding job (in particular the BKK based CAs) - they clearly showed their embarrassment because of the attitude of their supervisor.